The invention resides in an internal combustion engine with direct fuel injection having a cylinder closed by a cylinder head which includes a fuel injector for injecting fuel into the cylinder to generate a combustible mixture with air in the cylinder which is ignited by the spark of a spark plug.
In internal combustion engines with stratified charge direct fuel injection, fuel is injected by an injector directly into the combustion chamber of the cylinder in the area adjacent the spark plug. The mixture formed thereby is a relatively rich fuel/air mixture which can be easily ignited and whose combustion increases the temperature and pressure in the relatively lean mixture layers. This insures combustion of the leaner mixture while fuel consumption is reduced particularly in a low load engine operating range. The injector and the spark plug are arranged in the wall of the cylinder head delimiting the combustion chamber at an angle with respect to each other wherein the injector is preferably arranged in the center of the combustion chamber. Such an arrangement prevents that part of the fuel injected into the combustion chamber impinges directly onto the cylinder wall as this would cool, and accumulate, fuel on the cylinder wall resulting in an incomplete combustion and an increase in the emission of harmful products from the internal combustion engine.
DE 43 24 642 A1 discloses such a stratified charge direct fuel injection internal combustion engine with an injection nozzle arranged vertically in the center of the cylinder head. The injection nozzle injects fuel into the combustion chamber in a cone-like pattern whereby a combustible mixture is formed with combustion air which is separately supplied into the combustion chamber. The spark plug for the ignition of the mixture extends far into the combustion chamber such that the spark plug electrodes reach into the fuel cone and are wetted by fuel with each injection procedure and are cooled thereby. However, in time, deposits, particularly carbon deposits, are formed on the electrodes whereby the development of a spark between the electrodes is inhibited and the spark plug may finally fail completely.
It is therefore the principal object of the present invention to provide a direct fuel injection internal combustion engine which operates in an optimal manner over a long period of time. It is also an object of the invention to provide an internal combustion engine with direct fuel injection which generates in the combustion chamber a stratified charge which can be reliably ignited by the spark plug electrodes also at the edge of, or outside, the rich fuel mixture cone.